Jubilant Iranians raise hands and cheer during street celebrations following a landmark nuclear deal in Tehran, Iran, Tuesday, July 14, 2015. Iranians who have protested the deal were largely silent once it finally came through, even though opponents had previously vocalized their discontent.

Tehran, Iran — When the nuclear deal with Iran was reached on July 14, the street celebrations began. Many Iranians were jubilant, hopeful their crippled economy would soon improve, that Iran would reengage with the West – and that decades of US-Iran hostility might finally ease.

In other quarters, critics were not happy. Like their counterparts in Washington, they had spent most of two years noisily opposing the deal – and denouncing any compromise with a perennial enemy.

But even as the criticism in Washington turned into a louder roar – those vocal opponents here in Tehran were largely silent, for a time.

How that constituency was handled provides insight into the mechanisms used by the Islamic Republic – when expedient – to control hard-line voices, voices that almost always are ultimately loyal to Iran’s supreme leader, Ayatollah Ali Khamenei.

It also shows the challenge of trying to balance the fact of the deal against the expectations of true-believer revolutionaries – a relative minority, bred on flag-burning anti-Americanism, for whom direct US talks are an inconceivable shift from a pillar of Iran’s 1979 Islamic revolution.

“The government used every instrument they had to control reactions,” says Mojtaba Mousavi, editor of the website Iran’s View, who is close to conservative circles. “Any government would have used them, but the difference is that [President Hassan] Rouhani used them so much – very powerfully and very strictly. If the supreme leader didn’t intervene, they could have closed it all off.”

The signals have been clear: Iran’s Supreme National Security Council, which is presided over by the president, ruled in late June that reporting on the nuclear deal should be “restricted,” and letters were sent to media offices warning of tough consequences, including legal action, for “completely opposing the deal,” according to Iranian news reports.

“Those forces that most distrust the US can’t overnight adapt themselves to this situation…. They need more time,” says Kayhan Barzegar, director of the Institute for Middle East Strategic Studies in Tehran, noting how the deal has elicited a surge in Iran’s domestic politics before parliamentary elections next February.

Revival of public criticism

The struggle by critics in Iran mirrors the fight between President Barack Obama and Congress, and is even spurred by the US debate to a degree, he says. But like Mr. Obama in Washington, Mr. Rouhani “has the upper hand” in Iran.

“It is very hard to think that these forces can stop the implementation of the deal,” says Mr. Barzegar.

“This new dynamic in the US itself heats the debate inside Iran … and gives legitimacy to the process.”

The result in Iran has been a revival of public criticism, in part attributed to Mr. Khamenei. He supported the negotiations and called Iran’s team “sons of the revolution,” which helped keep criticism in check. But he has hinted that he is not satisfied with every aspect of the deal, and has said the hard-liner-dominated parliament – which strongly opposes Rouhani’s agenda – should “have their say.”

A special review commission, its 15 members almost entirely fundamentalist MPs opposed to the deal, began work Aug. 22. This week they heard former nuclear negotiator Saeed Jalili – who made little progress in talks during his tenure – claim that the deal crosses many red lines and forfeits “approximately 100 absolute rights.”

Keep fighting 'arrogance'

Portions of Mr. Jalili’s testimony were not broadcast on state television, prompting complaints from opponents of the deal.

But the commission's work has helped reenergize critics, from Revolutionary Guard commanders to hard-line editors, whose words have aimed to tarnish the deal in the public eye. One headline this week in Javan newspaper: "Shaking hands with America means departure from the discourse of Islamic Revolution."

“If the nuclear deal is approved or not, the Islamic Republic’s point of view – our Iranian point of view – toward arrogance [the US and Israel] will not change,” says Mikaeel Dayyani, leader of a student group of basiji, a volunteer resistance force known for rigorous religious training. “That is why this group is criticizing and doing so peacefully, because they know this will not change.”

“The government is trying to build up relations with the West and all countries, but this doesn’t mean that the nation will forget,” says Mr. Dayyani. In July he took part in a student meeting with Khamenei, directly asked the question, and was reassured that path would not change.

“When you see that the point of the country is to fight arrogance, it reduces your fears,” he says.

Keeping the revolution, and the deal, alive

And yet, other signals indicate that engagement is under way. On Aug. 23, the British Embassy in Tehran reopened under exceptionally heavy police guard, ensuring no hard-line protest. The embassy had been closed since it was stormed by protesters in November 2011, prompting a broader European diplomatic exodus that symbolized Iran’s isolation.

“There is a lack of demonstrations, a sign that these groups know they should not go out and protest,” says a veteran analyst in Tehran who asked not to be named. “Otherwise, we would see them in front of parliament, the president’s office, the UN.”

Instead, the protest has been limited to the parliamentary commission, he says, “not on the streets, which could get out of control.” So far that balance has been deftly achieved “to keep the revolution alive, but not going too far to damage the deal.”

“This has caused an earthquake,” says the analyst. “The damage control is to make it appear that they are still following the revolutionary path. But this is hard to swallow for many, that making a deal with America is not un-revolutionary. And [selling] this is Mr. Khamenei’s hard job.”